community/py3-lxml: add secfixes info for CVE-2021-43818

https://security.alpinelinux.org/vuln/CVE-2021-43818
(cherry picked from commit e54a8aca)

community/py3-lxml/APKBUILD

@@ -14,6 +14,8 @@ source="https://files.pythonhosted.org/packages/source/${_pkgname:0:1}/$_pkgname
 builddir="$srcdir/$_pkgname-$pkgver"
 
 # secfixes:
+#   4.6.5-r0:
+#     - CVE-2021-43818
 #   4.6.2-r0:
 #     - CVE-2020-27783
 #   4.6.3-r0: